Not all of them are plastic. You can still find some of the good old wood ones with heavy duty steel legs.
You got it, the particle board folding table available at kmart, Home Depot or anywhere fine furniture is sold. To OP, the table is rectangular and the legs fold out on either end. They come in different lengths. They are used at bazaars or when people are serving a lot of food. I used one for years because I couldn't get a desk in the closet that I called an office. They work great and they are relatively easy to carry.